//<p>给定一个二叉树，判断它是否是高度平衡的二叉树。</p>
//
//<p>本题中，一棵高度平衡二叉树定义为：</p>
//
//<blockquote>
//<p>一个二叉树<em>每个节点 </em>的左右两个子树的高度差的绝对值不超过 1 。</p>
//</blockquote>
//
//<p> </p>
//
//<p><strong>示例 1：</strong></p>
//<img alt="" src="https://assets.leetcode.com/uploads/2020/10/06/balance_1.jpg" style="width: 342px; height: 221px;" />
//<pre>
//<strong>输入：</strong>root = [3,9,20,null,null,15,7]
//<strong>输出：</strong>true
//</pre>
//
//<p><strong>示例 2：</strong></p>
//<img alt="" src="https://assets.leetcode.com/uploads/2020/10/06/balance_2.jpg" style="width: 452px; height: 301px;" />
//<pre>
//<strong>输入：</strong>root = [1,2,2,3,3,null,null,4,4]
//<strong>输出：</strong>false
//</pre>
//
//<p><strong>示例 3：</strong></p>
//
//<pre>
//<strong>输入：</strong>root = []
//<strong>输出：</strong>true
//</pre>
//
//<p> </p>
//
//<p><strong>提示：</strong></p>
//
//<ul>
//	<li>树中的节点数在范围 <code>[0, 5000]</code> 内</li>
//	<li><code>-10<sup>4</sup> <= Node.val <= 10<sup>4</sup></code></li>
//</ul>
//<div><div>Related Topics</div><div><li>树</li><li>深度优先搜索</li><li>二叉树</li></div></div><br><div><li>👍 874</li><li>👎 0</li></div>
  
package leetcode.editor.cn;

import com.sun.tools.javac.util.RichDiagnosticFormatter;

public class _110_BalancedBinaryTree{
    public static void main(String[] args) {
         Solution solution = new _110_BalancedBinaryTree().new Solution();
    }
    //leetcode submit region begin(Prohibit modification and deletion)
/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public boolean isBalanced1(TreeNode root) {
        if (root==null) {
            return true;
        }
        return dfs(root)!=-1;
    }

    private int dfs(TreeNode root) {
        if (root == null) {
            return 0;
        }
        int left = dfs(root.left);
        if (left == -1) {
            return -1;
        }
        int right= dfs(root.right);
        if (right == -1) {
            return -1;
        }
        return Math.abs(left-right)>1?-1:1+Math.max(left, right);
    }

    public boolean isBalanced(TreeNode root) {
        if (root == null) {
            return true;
        }
        return getHeight(root) != -1;
    }

    private int getHeight(TreeNode root) {
        if (root == null) {
            return 0;
        }
        int left = getHeight(root.left);
        if (left==-1) {
            return -1;
        }
        int right = getHeight(root.right);
        if (right == -1) {
            return -1;
        }
        if (Math.abs(left-right)>1) {
            return -1;
        }
        return 1+Math.max(left, right);
    }
}
//leetcode submit region end(Prohibit modification and deletion)

}